1. Field of the Invention
The invention is related to the field of communications, and in particular, to IMS call control nodes and methods that converge Application Server (AS) logic and gateway logic for providing online charging in IMS networks.
2. Statement of the Problem
As set forth in the 3rd Generation Partnership Project (3GPP), an IP Multimedia Subsystem (IMS) provides a common core network having an access-agnostic network architecture for converged networks. Service providers are accepting this architecture in next generation network evolution. Providing efficient IMS online charging for operator revenue generation is important to the successful deployment of IMS networks.
Several 3GPP technical specifications describe online charging for IMS networks. For instance, the 3GPP TS 32.200 specification describes an online charging server (OCS) having a session charging function. The OCS is coupled to a call session control function (CSCF) through an IMS service control (ISC) interface. The CSCF controls a call session for a calling party or called party and needs to communicate with the OCS over the ISC interface to provide online charging for the call session. However, an ISC interface is a service interface and does not support online charging. Therefore, in order to use the ISC interface between the CSCF and the OCS for online charging, additional functionality would unfortunately need to be added to the OCS.
In order to avoid overloading the OCS with additional functionality and to keep the online charging architecture consistent, the interface between the CSCF and the OCS may be changed to support online charging instead of adding functionality to the OCS. One option for an interface that supports online charging is to extend the ISC interface to allow for charging mechanisms. The ISC interface would then be both a service interface and a charging interface. Unfortunately, using the ISC interface as a hybrid service/charging interface may not be acceptable for standardization desired by the 3GPP.
Another option is to use the Ro interface instead of the ISC interface because the Ro interface already supports online charging. The 3GPP TS 32.296 specification suggests using the Ro interface for online charging by introducing an IMS gateway function that acts as a gateway between the CSCF and the OCS. The IMS gateway function as suggested in the 32.296 specification communicates with the CSCF over the ISC interface and communicates with the OCS over the Ro interface. Unfortunately, the 32.296 specification and the other 3GPP specifications do not describe how to use the IMS gateway function for online charging. For instance, the specifications do not define how the IMS gateway function is to operate to provide online charging. The specifications also do not resolve how the ISC interface, the Ro interface, and the CSCF would function together. For instance, the specifications state that whether the CSCF is directly connected to the OCS via a gateway (IMS gateway function) is beyond the scope of the standardization. The physical position of the IMS gateway function is in confusion in the specifications.
The specifications also describe the IMS network as including a plurality of application servers that are connected to an event-based charging function in the OCS. The application servers communicate with the OCS via an Ro interface, and communicate with the CSCF via an ISC interface. Unfortunately, the specifications do not define how the application servers communicate with the OCS to provide for session-based online charging for services.
The current 3GPP specifications do not adequately define how online charging may be accomplished for IMS networks. A problem remains for defining the functionality to enable online charging for IMS networks.